1. Field of Invention
The present invention relates to nuclear well logging to determine the salinity of water flowing either within or behind casing in a well borehole.
2. Description of Prior Art
U.S. Pat. Nos. 4,032,778; 4,032,779 and 4,032,780 of common ownership describe techniques for measuring water flow within or behind wellbore casing. The flowing water is irradiated with 14 MeV neutrons produced in an accelerator in a downhole sonde. The radioactive isotope nitrogen 16 induced in water through the O.sup.16 (n,p)N.sup.16 reaction is measured in energy and intensity with two detectors in the sonde so that the direction, linear flow velocity, volume flow rate and radial position of the center of water flow can be detected.
When water channels behind casing in the vicinity of the well borehole, it is of interest to define both the zone or zones from which the water is flowing and the zone or zones into which the water flows. Where the distance of the center of the flow channel is less than the maximum depth of investigation from the sonde, usually on the order of eight inches or so, the flow source zone can be located and flow can be usually followed. However, there are also situations where the entry or exit point of channeling water is outside of the maximum depth of investigation. Identification of the source of channeling water is of interest to a reservoir engineer.